Method of manufacturing engine cradles

ABSTRACT

A method for forming a structural member, the method comprising the steps of placing a first sheet member having a length dimension greater than a width dimension in a press, placing a second sheet member having a length dimension greater than a width dimension in the press, the second member only partially overlapping the first member, the first member only partially overlapping the second member, and the direction of the length dimension of the second member being angled relative to the direction of the length dimension of the first member, and closing the press to shape the first member and the second member.

BACKGROUND OF THE INVENTION

The invention relates to structural members and to methods ofmanufacturing structural members. More particularly, the inventionrelates to structural frames for motor vehicles, as well as othervehicle structural elements, such as control arms and door panels. Stillmore particularly, the invention relates to engine cradles for passengervehicles.

A typical engine cradle for a passenger vehicle comprises fourstructural frame members welded together to define a generallyrectangular opening. Each structural member has a box-like crosssection. The box-like section can be made, for example, by welding apair of U-shaped members together.

Known methods of manufacturing engine cradles require a substantialcapital investment and substantial manpower. It is also very difficultto control tolerances on the various cradle parts because of thesignificant number of operations required to make the cradle. Thetolerances of each of these sequential operations may stack to causelarge dimensional discrepancies in the finished assembly.

SUMMARY OF THE INVENTION

The invention provides an improved method of manufacturing structuralmembers and structural frame members. More particularly, the inventionprovides an improved method of manufacturing engine cradles forpassenger vehicles. The invention also provides improved structuralmembers and an improved engine cradle for passenger vehicles.

Preferably, four elongated sheet metal blanks are formed and punchlockedtogether with a single stroke of a stamping press. The sheet metalblanks, which will be referred to as "top sheets," are placed in thepress with first and second sheets parallel and spaced apart. A thirdsheet is located with one end overlapping a portion of the first sheetand with the opposite end overlapping a portion of the second sheet. Thefourth sheet is placed in the press with one end overlapping a portionof the first sheet and with the opposite end overlapping a portion ofthe second sheet. The fourth sheet is parallel to and spaced from thethird sheet, so that the four top sheets define a rectangle. A firstreinforcement blank is placed below the overlapping portions of thefirst and third sheets, and extends aft to give doubled metal stock atthe rear body mount, and a second reinforcement blank is placed belowthe overlapping portions of the second and third sheets, and issimilarly extended. The press is then closed so that the top sheets andthe reinforcement blanks are formed and secured together with a singlepress stroke.

Each of the four top sheets is formed in this first press operation soas to have a hat-shaped cross section with a generally horizontal topwall, generally vertical side walls extending downwardly from theopposite edges of the top wall, and generally horizontal flangesextending outwardly from the bottom edges of the side walls. A joint isformed between two formed top sheets at each point where the sheetsoverlap. Two of the joints are formed by integral extensions of the sidewalls of one of the connected sheets being bent outwardly andoverlapping the side walls of the other sheet, by an integral extensionof the top wall of the one sheet overlapping the top wall of the othersheet, by spaced integral extensions of the side wall of the other sheetbeing bent outwardly and extending inside the side walls of the onesheet, and by an integral extension of the top wall of the other sheetextending beneath the top wall of the one sheet. The connected sheetsare secured together by friction from coincident forming and punch-locksin the overlapping top wall extensions. The other two joints are formedby integral extensions of the side wall of one sheet being bentoutwardly and overlapping the ends of the side walls of the other sheet,by an integral extension of the top wall of the one sheet overlappingthe top wall of the other sheet, and by integral extensions of oneflange of the one sheet overlapping the flanges of the other sheet. Thefirst and second top sheets are also punch-locked to the respectivereinforcement blanks.

Next, the assembly of the four top sheets and the reinforcement blanks(the "first operation assembly") is placed, along with four additionalsheet metal blanks which will be referred to as "closing sheets," ineither a second press or the same press with a different die. Eachclosing sheet is shaped so as to be co-extensive with the underside of arespective one of the formed top sheets. The four closing sheets areplaced in the second die in substantially the same orientation as werethe four top sheets. The first operation assembly is then placed overthe four closing sheets so that the flanges of each formed top sheetrest on a respective one of the closing sheets. The press is then closedso as to punch-lock the flanges of each formed top sheet to theunderlying closing sheet. The result is a structural frame with fourbox-like members defining a rectangular or trapezoidal opening.

After the two press operations, the frame is taken to a final assemblyfixture where critical joints are welded and brackets are attached.Preferably, joints between overlapping top sheets and joints betweenoverlapping closing sheets are arc welded.

A principal feature of the invention is the provision of a manufacturingmethod that requires substantially less manpower, substantially lesscapital investment and substantially less floor space than conventionalmethods. For example, while a conventional method requires 10 die lines,30 press strokes, 15 operators and 14,000 square feet to manufacture aparticular engine cradle from blanks to the final assembly fixture, themethod of the invention requires two press strokes, four operators and1,200 square feet to similarly manufacture an equivalent engine cradle.A variation of the later can use automatic blank and part feed toeliminate all of the direct labor, while using 1,500 square feet ofspace, and the same two press strokes. The result is an engine cradlethat is significantly less expensive to manufacture.

Also, prior art methods required major structural components to bealigned while being welded. This involves a stacking of the tolerancesof the 10 detail parts and then of some 4 sub-assemblies. This can makeit difficult to maintain tolerances. In the method of the invention, themajor structural components are secured together by the die beforewelding. Tolerances are therefore virtually as good as the die. Lapwelds can then be completed on mating surfaces which are in intimatecontact as a result of the forming process. In other words, there wouldbe no weld gaps.

Conventional methods also frequently rely on post assembly operations toprecisely produce, such as by post pierce operations, holes in thestructural member for attaching vehicle components to the member. In theinvention, needed holes can be placed in the sheet members prior toassembly, or formed in the structural member in the second stage of atwo stage press, thereby eliminating the need to have post pierceoperations.

Other features and advantages of the invention will become apparent tothose skilled in the art upon review of the following detaileddescription, claims and drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of upper and lower die halves andsix sheet metal blanks employed in a first press operation in accordancewith the invention.

FIG. 2 is an elevational view of a press utilizing the upper and lowerdie halves.

FIG. 3 is a top plan view of the blanks properly arranged for forming inthe first press operation.

FIG. 4 is an exploded perspective view of the formed and joined blanksafter the first press operation along with four closing sheet blanksemployed in a second press operation.

FIG. 5 is an exploded perspective view of the blanks shown in FIG. 4after the second press operation and after arc welding of criticaljoints, along with additional brackets.

FIG. 6 is a view taken along line 6--6 in FIG. 1.

FIG. 7 is a view taken along line 7--7 in FIG. 5.

FIG. 8 is a view taken along line 8--8 in FIG. 5.

FIG. 9 is a view taken along line 9--9 in FIG. 4.

FIG. 10 is an enlarged sectional view showing three blanks being punchedlocked in the first press operation.

FIG. 11 is a view taken along line 11--11 in FIG. 4.

FIG. 12 is an enlarged partial perspective view of the assembly formedby the first press operation.

FIG. 13 is a partial perspective view of a formed blank that is part ofan alternative embodiment of the invention.

FIG. 14 is a partial perspective view of an engine cradle that is analternative embodiment of the invention.

FIG. 15 is a partial perspective view of an engine cradle that isanother alternative embodiment of the invention.

Before one embodiment of the invention is explained in detail, it is tobe understood that the invention is not limited in its application tothe details of the construction and the arrangements of components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is to be understood that thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A structural member such as an engine cradle 10 (see FIG. 5) ismanufactured as follows in accordance with the invention. A stampingpress 14 employed in the manufacturing process is illustrated in FIG. 2.The press 14 itself is conventional and will not be described in detail.As is known in the art, the press 14 can be closed to move upper andlower die halves 18 and 22 together.

The die halves 18 and 22 are illustrated in greater detail in FIG. 1.The upper die half 18 has therein a recess 26, and the lower die half 22has thereon a complementary projection 30. The projection 30 has thereon(see FIGS. 1 and 6) pins 34 which, as is known in the art, move intorecesses (not shown) in the upper die half 18 when the press 14 isclosed so as to orient blanks on the lower die half 22, as will beexplained hereinafter.

As shown in FIGS. 1 and 3, six sheet metal blanks or members 41, 42, 43,44, 45 and 46 are placed on the lower die half 22. The blanks 41, 42, 43and 44 are elongated and are referred to hereinafter as "top sheets." By"elongated" it is meant that each top sheet 41, 42, 43 or 44 has (seeFIG. 3) a longitudinal axis 50 and a maximum length dimension greaterthan its maximum width dimension. The sheets 41 and 42 are generallyparallel and spaced apart, and the sheets 43 and 44 are generallyparallel and spaced apart. Thus, the longitudinal axes 50 of the sheets41 and 42 are transverse to the longitudinal axes 50 of the sheets 43and 44. In other words, the length dimensions of the sheets 41 and 42are angled relative to the length dimensions of the sheets 43 and 44.The axes 50 of the sheets 41 and 42 are preferably perpendicular to theaxes 50 of the sheets 43 and 44. As best shown in FIG. 3, one end of thesheet 41 partially overlaps the sheet 43, the opposite end of the sheet41 partially overlaps the sheet 44, and spaced portions of the sheet 42partially overlap ends of the sheets 43 and 44. It should be noted thatnone of the sheets 41, 42, 43 and 44 is completely overlapped by anothersheet.

The blanks 45 and 46, referred to hereinafter as "reinforcement blanks,"are also placed on the lower die half 22. The reinforcement blank 45 islocated beneath an end of the sheet 43, and the reinforcement blank 46is located beneath an end of the sheet 44.

Each of the top sheets 41, 42, 43 and 44 and each of the reinforcementblanks 45 and 46 has there through (see FIG. 1) one or more apertures54. Each aperture 54 receives (see FIG. 6) a respective pin 34 on thelower die half 22. The pins 34 orient the top sheets 41, 42, 43 and 44and reinforcement blanks 45 and 46 relative to the die half 22, as isknown in the art. One edge of the sheet 42 has therein (see FIG. 1)spaced indentations 58, and one edge of each of the sheets 43 and 44 andthe reinforcement blanks 45 and 46 has therein an indentation 58. Thereason for the indentations 58 is explained below.

After the top sheets 41, 42, 43 and 44 and the reinforcement blanks 45and 46 are properly located on the lower die half 22, the press 14 isclosed. Closing of the press 14 forms the top sheets 41, 42, 43 and 44and the reinforcement blanks 45 and 46 into an assembly 62 that isillustrated in FIG. 4. More particularly, each of the top sheets 41, 42,43 and 44 is formed so as to have a hat-shaped cross section alongsubstantially the entire length thereof. The cross sections of thesheets 41, 42, 43 and 44 are substantially identical, and only the crosssection of the sheet 43 will be described in detail.

The hat-shaped cross section of the sheet 43 is illustrated in FIG. 11.The top sheet 43 is formed so as to have a generally planar top wall 66with opposite edges 70 and 74 extending parallel to the longitudinalaxis 50 of the formed sheet. The sheet 43 also has a generally planarside wall 78 extending downwardly from the edge 70 of the top wall 66,and a generally planar side wall 82 extending downwardly from theopposite edge 74 of the top wall 66. The side walls 78 and 82 aregenerally perpendicular to the top wall 66, although the side walls 78and 82 preferably diverge slightly, as shown in FIG. 11. Each of theside walls 78 and 82 has a lower edge 86. The top sheet 43 also has aflange 90 extending outwardly from the lower edge 86 of the side wall78, and a flange 94 extending outwardly from the lower edge 86 of theside wall 82. The flanges 90 and 94 are generally co-planar and parallelto the top wall 66.

As shown in FIG. 4, the sheet 42 is also formed to have an end wall 98extending downwardly from one end of the top wall 66, and an end wall(not shown) extending downwardly from the opposite end of the top wall66. The lower end of each end wall 98 has thereon an outwardly extendingflange 102.

Closing of the press 14 forms (see FIG. 4) a joint 106 between theformed sheets 41 and 43, a joint 110 between the formed sheets 41 and44, a joint 114 between the formed sheets 42 and 43, and a joint 118between the formed sheets 42 and 44.

At the joints 106 and 110, as shown in FIGS. 4 and 12, integralextensions 122 of the side walls 78 and 82 of the sheet 41 are bentoutwardly and overlap side walls of the sheets 43 and 44, integralextensions 126 of the top wall 66 of the sheet 41 overlap the top walls66 of the sheets 43 and 44, and integral extensions 130 (only one isshown) of the flanges 90 and 94 of the sheet 41 overlap flanges of thesheets 43 and 44. Additionally, referring to FIG. 12 in which the joint110 is shown, an integral extension 131 of the top wall 66 of the sheet44 extends beneath the top wall of the sheet 41, and integral extensions132 of the side wall 78 of the sheet 44 are bent outwardly and extendgenerally perpendicular to the side wall 78 of the sheet 44 and insidethe side walls 78 and 82 of the sheet 41. The joint 106 is similarlyformed and will not be described in detail.

At the joints 114 and 118 (see FIG. 4), integral extensions 134 (two areshown) of the side wall 82 of the sheet 42 are bent outwardly andoverlap the ends of the side wails of the sheets 43 and 44, integralextensions 138 of the top wall 66 of the sheet 42 overlap the top walls66 of the sheets 43 and 44, and integral extensions 142 (two are shown)of the flange 94 of the sheet 42 overlap the flanges of the sheets 43and 44.

Closing of the press 14 forms each of the reinforcement blanks 45 and 46into an inverted U-shape, as best shown in FIG. 9, with eachreinforcement blank having a top wall 146 abutting the underside of thetop wall 66 of the associated top sheet, a downwardly extending flange150 abutting the inside of one side wall of the associated top sheet,and a downwardly extending flange 154 abutting the inside of the otherside wall of the associated top sheet.

The indentations 58 in the top sheets 42, 43 and 44 and in thereinforcement blanks 45 and 46 provide (see FIGS. 7 and 8) openings 158in the side walls of the formed sheets 42, 43 and 44. The openings 158in the formed sheet 42 (see FIG. 8) receive the ends of the formedsheets 43 and 44, and the openings 158 in the sheets 43 and 44 (see FIG.7) are aligned with the ends of the sheet 41. Thus, the inside of eachof the formed sheets 41, 42, 43 and 44 is open to the inside of theadjacent sheets. Without the indentations, the stretch in these openingswould be too great and forming splits would occur.

In addition to forming the top sheets 41, 42, 43 and 44 and thereinforcement blanks 45 and 46 as described above, the first pressoperation also forms (see FIGS. 4, 5 and 8) punch-locks 162 between thetop wall 66 of the sheet 43 and the overlapping extension 138 of the topwall 66 of the sheet 42, punch-locks 162 between top wall 66 of thesheet 44 and the overlapping extension 138 of the top wall 66 of thesheet 42, punch-locks 164 between the reinforcement blank 45, the topwall 66 of the sheet 43, and the overlapping extension 126 of the topwall 66 of the sheet 41, punch-locks 164 between the reinforcement blank46, the top wall 66 of the sheet 44, and the overlapping extension 126of the top wall 66 of the sheet 41, punch-locks 166 between the top wall66 of the sheet 43 and the top wall of the reinforcement blank 45, andpunch-locks 166 between the top wall 66 of the sheet 44 and the top wallof the reinforcement blank 46. The punch-locks 162, 164 and 166 arecreated by respective punch-lock mechanisms 170, one of which isillustrated in FIG. 10. Such a punch-lock mechanism is known in the artand will not be described in greater detail. Suitable punch-lockmechanisms are disclosed in U.S. Pat. Nos. 3,359,935 and 3,579,809, bothof which are incorporated herein by reference. In other embodiments,other securing means such as adhesives, spot welds, or other clinchingshapes may be used.

In the preferred embodiment, the punch-locks are installed by mechanicalor hydraulic means at the bottom of the form stroke, after the metalforming to shape is completed, but while the form tool still fixturesthe parts in perfect alignment. This is done by the use of a two-stagepress, as is conventionally known in the art. In addition, the secondstage operation can be used to pierce holes in the frame, such as thebody mount opening 47 shown in FIG. 4.

Along with being punch-locked together, adjacent members of the assembly62 formed by the first press operation are also held together byfrictional contact of the shaped overlapped portions of the members.

After the first press operation, the assembly 62 created thereby isplaced in a press with a different die (not shown). This press can beeither the press 14 or a different press. Also placed in the press are(see FIG. 4) four elongated sheet metal blanks 181, 182, 183 and 184referred to hereinafter "closing sheets." The closing sheets 181, 182,183 and 184 are located in the press in a manner similar to that inwhich the top sheets 41, 42, 43 and 44 were located in the press 14. Theopposite ends of the closing sheet 181 partially overlap the closingsheets 183 and 184, and the closing sheet 182 partially overlaps theends of the sheets 183 and 184. The sheets 181, 182, 183 and 184 aresubstantially the same size and shape as the bottoms of the formedsheets 41, 42, 43 and 44, respectively. After the closing sheets 181,182, 183 and 184 are located in the press, the assembly 62 formed in thefirst press operation is placed on top of the closing sheets 181,182,183 and 184 so that the flanges of the formed top sheets 41, 42, 43 and44 rest on top of the closing sheets 181,182, 183 and 184, respectively.Pilot pins (not shown) may be used to align the assembly 62 relative tothe closing sheets. The press is then closed. Closing of the two-stagepress forms punch-locks 190 (see FIG. 5) between the flanges of theformed top sheets 41, 42, 43 and 44 and the closing sheets 181,182, 183and 184. This closes the underside of each of the formed top sheets 41,42, 43 and 44 and creates an assembly of four elongated, box-shapedstructural frame members.

After the second press operation, the assembly created thereby is takento a final assembly fixture (not shown) where the joints between topsheets 41, 42, 43 and 44 and the joints between closing sheets are arcwelded (indicated by reference numeral 192 in FIG. 5) and where bracketscan be attached to the assembly. Brackets 194 and 198 are shown weldedto the assembly in FIG. 5. The arc welding of the overlap joints of theformed top sheet is greatly assisted by the perfect lap fit-ups createdby their coincident forming.

A formed top sheet 200 which is an alternative embodiment of theinvention is partially illustrated in FIG. 13. Except as describedbelow, the top sheet is identical in cross-section to the top sheets 41,42, 43 and 44, and common elements have been given the same referencenumerals.

The top sheet 200 differs from the top sheets 41, 42, 43 and 44 in thateach of the side walls 78 and 82 has therein spaced, indentations 204such that the flanges 90 and 94 have sections of increased and decreasedwidth alternately spaced along the length thereof. During the secondpress operation, punch-locks are formed adjacent the indentations 204.In other words, the flange sections of increased width are attached tothe closing sheet.

An engine cradle 300 which is another alternative embodiment of theinvention is partially illustrated in FIG. 14. The engine cradle 300differs from the engine cradle 10 in that the engine cradle 300 includesa kicked-up portion 304. The kicked-up portion 304 is formed byproviding curved, rather than planar, mating walls of the die halvesused in the first and second press operations. Alternatively, in apreferred process, the blanks for both the top and bottom sheets arepreformed to the same curved shape in a two stage blanking operationprior to the first press stroke.

An engine cradle 400 which is another alternative embodiment of theinvention is partially illustrated in FIG. 15. The engine cradle 400differs from the engine cradle 10 in that the structural members have atriangular cross section rather than a rectangular cross section. Asshown in FIG. 15, the members 41 and 44 have side walls 78 and 82 whichare connected directly to each other at their upper edges. Thus, eachmember has a top 404, a side wall 78 extending downwardly from the top404, a side wall 82 extending downwardly from the top 404, a flange 90extending outwardly from the side wall 78, and a flange 94 extendingoutwardly from the side wall 82. At the illustrated joint, integralextensions 122 of the side walls 78 and 82 of the member 41 are bentoutwardly and overlap the side wall 78 of the member 44, integralextensions 132 of the side wall 78 of the sheet 44 are bent outwardlyand extend generally perpendicular to the side wall 78 of the sheet 44and inside the side walls 78 and 82 of the sheet 41, and integralextensions 130 of the flanges 90 and 94 of the sheet 41 overlap theflange 90 of the sheet 44.

Various features of the invention are set forth in the following claims.

We claim:
 1. A method for forming a structural member, said methodcomprising the steps of:placing a first sheet member having a lengthdimension greater than a width dimension in a die in a press, placing asecond sheet member having a length dimension greater than a widthdimension in said press, said second member only partially overlappingsaid first member, said first member only partially overlapping saidsecond member, and the direction of the length dimension of said secondmender being angled relative to the direction of the length dimension ofsaid first member, and closing said press, thereby attaching said firstmember to said second member and shaping each of said first member andsaid second member into a non-planar shape along substantially theentire length thereof.
 2. A method in accordance with claim 1 whereinsaid closing step shapes at least portions of said first and secondmembers in intimate contact with each other into a shape having a top,one side wall extending downwardly from said top, and another side wallextending downwardly from said top, one flange extending outwardly fromsaid one side wall, and another flange extending outwardly from saidother side wall.
 3. A method as set forth in claim 2 wherein saidclosing step further shapes said first and second members such that saidshape has a top wall extending between said side walls.
 4. A method inaccordance with claim 2 wherein said attaching occurs by frictionalcontact of the shaped overlapped portions of said members.
 5. A methodin accordance with claim 2 wherein said attaching occurs bypunch-locking one of said members relative to the other.
 6. A method inaccordance with claim 2 wherein said attaching occurs by punch-lockingone of said members relative to the other and by frictional contact ofthe shaped overlapped portions of said members.
 7. A method as set forthin claim 2 wherein said closing step also shapes said portions of saidfirst and second members to have one flange extending outwardly fromsaid one side wall, and another flange extending outwardly from saidother side wall.
 8. A method in accordance with claim 2 and furtherincluding the steps of:placing said first and second members in a seconddie in a press, placing at least a third sheet member in said second diein overlapping relationship with said flanges of at least one of saidfirst and second members, and closing said press, thereby attaching saidflanges of said one of said first and second members to said thirdmember and closing substantially all of the interior of said one of saidfirst and second members.
 9. A method in accordance with claim 8 whereinsaid first-mentioned closing step forms said side walls with spacedindentations such that said flanges have sections of increased anddecreased width alternately spaced along the length thereof, and whereinsaid second-mentioned closing step attaches said flange sections ofincreased width to said third member.
 10. A method in accordance withclaim 2 wherein said closing step shapes each of said first and secondsheet members into said shape along substantially the entire lengththereof, and wherein said method further includes the steps of:placingsaid first and second members in a second die in a press, placing firstand second closing sheet members in said second die, each of said firstand second closing sheet members being in overlapping relationship withsaid flanges of a respective one of said first and second members, andclosing said press, thereby attaching each of said flanges to therespective closing sheet member closing substantially all of theinterior of said first and second members.
 11. A method in accordancewith claim 10 wherein said first-mentioned closing step forms said sidewalls with spaced indentations such that said flanges have sections ofincreased and decreased width alternately spaced along the lengththereof, and wherein said second-mentioned closing step attaches saidflange sections of increased width to the respective closing sheetmember.
 12. A method in accordance with claim 10 and further includingthe steps of:taking said structural frame to a final assembly fixture,welding at least one joint between sheet members, and attaching bracketsto at least one of said sheet members.
 13. A method in accordance withclaim 1 wherein said closing step forms said structural member with akicked-up portion.
 14. A method in accordance with claim 1 wherein saidplacing steps include placing said first and second members in the pressso that only end portions of said first and second members overlap. 15.A method for forming a structural member, said method comprising thesteps of:placing a first sheet member having a length dimension greaterthan a width dimension in a die in a press, placing a second sheetmember having a length dimension greater than a width dimension in saidpress, said second member only partially overlapping said first member,said first member only partially overlapping said second member, and thedirection of the length dimension of said second member being angledrelative to the direction of the length dimension of said first member,placing a third sheet member having a length dimension greater than awidth dimension in the die, said third member only partially overlappingsaid second member, said second member only partially overlapping saidthird member, and the direction of the length dimension of said thirdmember being angled relative to the direction of the length dimension ofsaid second member, placing a fourth sheet member having a lengthdimension greater than a width dimension in the die, said fourth memberonly partially overlapping said third member and said first member, saidthird member only partially overlapping said fourth member, said firstmember only partially overlapping said fourth member, and the directionof the length dimension of said fourth member being angled relative tothe direction of the length dimension of said third member and thedirection of the length dimension of said first member so that a closedopening is formed between said four sheet members, and closing saidpress, thereby shaping said first, second third and fourth sheet membersinto a non-planar shape along substantially the entire length thereof.16. A method in accordance with claim 15 wherein said placing stepsinclude placing said first, second, third and fourth members in thepress so that only end portions of said first, second, third and fourthmembers overlap.
 17. A method for forming a structural member, saidmethod comprising the steps of:placing a first sheet member having alength dimension greater than a width dimension in a die in a press,placing a second sheet member having a length dimension greater than awidth dimension in said press, said second member only partiallyoverlapping said first member, said first member only partiallyoverlapping said second member, and the direction of the lengthdimension of said second member being angled relative to the directionof the length dimension of said first member, closing said press,thereby attaching said first member to said second member and shapingsaid first member and said second member such that at least portions ofsaid first and second members in intimate contact with each other have atop, one side wall extending downwardly from said top, another side wallextending downwardly from said top, one flange extending outwardly fromsaid one side wall, and another flange extending outwardly from saidother side wall, placing said first and second members in a second diein a press, placing at least a third sheet member in said second die inoverlapping relationship with said flanges of at least one of said firstand second members, and closing said press, thereby attaching saidflanges of said one of said first and second members to said thirdmember and closing substantially all of the interior of said one of saidfirst and second members.
 18. A method in accordance with claim 17wherein said first-mentioned closing step forms said side walls withspaced indentations such that said flanges have sections of increasedand decreased width alternately spaced along the length thereof, andwherein said second-mentioned closing step attaches said flange sectionsof increased width to said third member.
 19. A method for forming astructural member, said method comprising the steps of:placing a firstsheet member having a length dimension greater than a width dimension ina die in a press, placing a second sheet member having a lengthdimension greater than a width dimension in said press, said secondmember only partially overlapping said first member, said first memberonly partially overlapping said second member, and the direction of thelength dimension of said second member being angled relative to thedirection of the length dimension of said first member, closing saidpress, thereby attaching said first member to said second member andshaping said first member and said second member such that at leastportions of said first and second members in intimate contact with eachother have a shape having a top, one side wall extending downwardly fromsaid top, another side wall extending downwardly from said top, oneflange extending outwardly from said one side wall, and another flangeextending outwardly from said other side wall, wherein said closing stepshapes each of said first and second sheet members into said shape alongsubstantially the entire length thereof, placing said first and secondmembers in a second die in a press, placing first and second closingsheet members in said second die, each of said first and second closingsheet members being in overlapping relationship with said flanges of arespective one of said first and second members, and closing said press,thereby attaching each of said flanges to the respective closing sheetmember and closing substantially all of the interior of said first andsecond members.
 20. A method in accordance with claim 19 wherein saidfirst-mentioned closing step forms said side walls with spacedindentations such that said flanges have sections of increased anddecreased width alternately spaced along the length thereof, and whereinsaid second-mentioned closing step attaches said flange sections ofincreased width to the respective closing sheet member.
 21. A method inaccordance with claim 19 and further including the steps of:taking saidstructural member to a final assembly fixture, welding at least onejoint between sheet members, and attaching brackets to at least one ofsaid sheet members.
 22. A method for forming a structural member, saidmethod comprising the steps of:placing in a die in a press a firstelongated sheet member having a longitudinal axis, placing in said die asecond elongated sheet member having a longitudinal axis transverse tosaid longitudinal axis of said first member, said second member onlypartially overlapping said first member, said first member onlypartially overlapping said second member, and closing said press,thereby attaching said first member to said second member and formingeach of said first member and said second member into a non-planar shapealong substantially the entire length thereof.
 23. A method inaccordance with claim 22 wherein said closing step forms each of saidfirst and second members into a shape along substantially the entirelength thereof such that each of said members has a top, one side wallextending downwardly from said top, and another side wall extendingdownwardly from said top.
 24. A method in accordance with claim 23wherein said closing step forms each of said members with a top wallextending between said side walls.
 25. A method as set forth in claim 24wherein said closing step results in said top wall of said first memberbeing punch-locked to said top wall of said second member.
 26. A methodas set forth in claim 23 wherein said closing step attaches said membersto each other at a joint formed by integral extensions of one side wallof one of said members being bent outwardly and extending inside saidside walls of the other of said members.
 27. A method as set forth inclaim 23 wherein said closing step attaches said members to each otherat a joint formed by integral extensions of said side walls of one ofsaid members being bent outwardly and overlapping a side wall of theother of said members.
 28. A method as set forth in claim 23 whereinsaid closing step attaches said members to each other at a joint formedby integral extensions of one side wall of one of said members beingbent outwardly and overlapping said side walls of the other of saidmembers.
 29. A method as set forth in claim 23 wherein said closing stepalso forms said first and second members to have one flange extendingoutwardly from said one side wall, and another flange extendingoutwardly from said other side wall.
 30. A method in accordance withclaim 23 and further including the steps of:placing said first andsecond members in a second die in a press, placing first and secondclosing sheet members in said second die, each of said first and secondclosing sheet members being in overlapping relationship with saidflanges of a respective one of said first and second members, andclosing said press, thereby attaching each of said flanges to therespective closing sheet member closing substantially all of theinterior of said first and second members.
 31. A method in accordancewith claim 22 wherein said placing steps include placing said first andsecond members in the press so that only end portions of said first andsecond members overlap.
 32. A method for forming a structural member,said method comprising the steps of:placing in a die in a press a firstelongated sheet member having a longitudinal axis, placing in said die asecond elongated sheet member having a longitudinal axis transverse tosaid longitudinal axis of said first member, said second member onlypartially overlapping said first member, said first member onlypartially overlapping said second member, closing said press, therebyattaching said first member to said second member and forming each ofsaid first member and said second member into a shape alongsubstantially the entire length thereof such that each of said memberhas a top, one side wall extending downwardly from said top, anotherside wall extending downwardly from said top, one flange extendingoutwardly from said one side wall, and another flange extendingoutwardly from said other side wall, placing said first and secondmembers in a second die in a press, placing first and second closingsheet members in said second die, each of said first and second closingsheet members being in overlapping relationship with said flanges of arespective one of said first and second members, and closing said press,thereby attaching each of said flanges to the respective closing sheetmember and closing substantially all of the interior of said first andsecond members.
 33. A method for forming a structural member, saidmethod comprising the steps of:placing in a press first and second sheetmembers, said second member only partially overlapping said firstmember, said first member only partially overlapping said second member,and closing said press, thereby securing said second member to saidfirst member, forming said first member into a shape along substantiallythe entire length thereof such that said first member has a top, oneside wall extending downwardly from said top, and another side wallextending downwardly from said top, and forming said second member intoa non-planar shape along substantially the entire length thereof.
 34. Amethod as set forth in claim 33 wherein said closing step forms saidfirst member so as to have a top wall extending between said side walls.35. A method as set forth in claim 33 wherein said closing step formssaid first member so as to have one flange extending outwardly from saidone side wall, and another flange extending outwardly from said otherside wall.
 36. A method in accordance with claim 35 and furtherincluding the steps of:placing said first and second members in a seconddie in a press, placing a closing sheet member in said second die, saidclosing sheet member being in overlapping relationship with said flangesof said first mender, and closing said press, thereby attaching each ofsaid flanges of said first member to said closing sheet member andclosing substantially all of the interior of said first member.
 37. Amethod in accordance with claim 33 wherein said placing steps includeplacing said first and second members in the press so that only endportions of said first and second members overlap.
 38. A method forforming a structural member, said method comprising the steps of:placingin a press first and second sheet members, said second member onlypartially overlapping said first member, said first member onlypartially overlapping said second member, closing said press, therebysecuring said second member to said first member and forming at leastsaid first member into a shape along substantially the entire lengththereof such that said first member has a top, one side wall extendingdownwardly from said top, another side wall extending downwardly fromsaid top, one flange extending outwardly from said one side wall., andanother flange extending outwardly from said other side wall, placingsaid first and second members in a second die in a press, placing aclosing sheet member in said second die, said closing sheet member beingin overlapping relationship with said flanges of said first member, andclosing said press, thereby attaching each of said flanges of said firstmember to said closing sheet member and closing substantially all of theinterior of said first member.